You'll first need the ShoreTel Connect app. You can find that here.
You'll then go to preferences and it will take you to this page.
Next, click on "Call Routing" on the left sidebar. You will then select "also simultaneously ring these numbers"
Select the first drop down and fill in the blanks with the correct info. You can also select if you'd like to pick up using 1 or to automatically pick up. The first option will have an automated voice tell you the number that is calling you.
After finishing that info, you'll click "Use selected number". And then "next". You will land on a page that looks like this:
I would advise a minimum of 3 rings before forwarding to voicemail. After pushing next, you will be brought to a page labeled "FindMe". Click "Disabled". After this, you'll have 2 self explanatory steps and finally push Done.